The Synthesis And Characteristic Of Silver-palladium Alloy And Silver

In this experiment, the submicron-size powders used for conductive-paste were prepared by Liquid Chemical Reduction Method with silver nitrate palladium nitrate as precursor.The obtained powders were able to meet the requirements of the conductive paste by optimizing the reaction conditions to control the particle’s morphology,size,size distribution, loose density, tap density and other properties.Scanning electronic microscope (SEM) was used to characterize the morphology of powders,the structure was analyzed by X-ray Diffraction(XRD),and the particle size distribution was analyzed by centrifugal sedimentation method.In addition,the possible the experimental system’s growth mechanism of the powders was also discussed.(1)The optimal parameter is that formaldehyde was used as reductant,AgNO3concentration is0.100-0.1300mol/L,mole ratio of oxidant to reductant is (2-4):1,pH value of the solution is10-11, PVP was used as dispersant(wt%=3%),mixed by adding oxidant to reductant,the mixing time was45-55min.The study indicated,in the process of preparing silver powders by liquid chemical reduction method with formaldehyde as reductant and PVP as dispersant,the solution’s pH value were the crucial influencing factors of silver particle’s morphology,size and size distributing;and the surface is relatively rough the mean silver particle size decreased,the final particles appears regular polyhedron with the increase of the pH value of the solution.(2)Hydrazine hydrate was used as reductant to AgNO3/Pd(NO3)2(Ag/Pd=7:3),AgNO3concentration is0.083-0.3532mol/L,mole ratio of oxidant to reductant is (2-1):1,pH value of the solution is10-11adjusted by strong aqua ammonia,gum arabic was used as dispersant (wt%=1-2.5%),mixed with symmetric way,and the mixing time was90-120min.In following time,heat treated at500℃for3hours, the mean particle size would be500nm-1μm.(3)Ascorbic acid was used as reductant to AgNO3/Pd(NO3)2(Ag/Pd=7:3),AgNO3concentration is0.083-0.3532mol/L,the mole ratio of oxidant to reductant is (2-1):1,pH value of the solution is1.8-2.3adjusted by sodium hydroxide,gum arabic was used as dispersant (wt%=5-10%), mixed with symmetric way, the mixing time was60-80min.In following time, heat treated at500℃for3hours, the mean particle size would be300nm-600nm..The ultimate product would be pure、good crystallize and well dispersed.The mixing way, the mixing time,the kinds and concentration ratio of dispersant also affect the Ag-Pd particle’s morphology.